Indicator device for bearing failures in drill bits



RELATIVE BEARING WEAR (PERCENT) Nov. 6, 1962 Filed May 9, 1960 IIIIUIIII 2 Sheets-Sheet l /BEARING WEAR o 25 c 50 75 A X LBEARING TEMPERATURE I I l I I I I I FIG.

BIT

6 INCREASE ROTATING TIME FIG.I

INVENTORS F.J.TOTH

o. F. TOOMEY BY .l-k-

HEIR AGE INCREASE BEARING TEMPERATURE Nov. 6, 1962 F. J. TOTH ETAL INDICATOR DEVICE FOR BEARING FAILURES IN DRILL BITS 2 Sheets-Sheet 2 Filed May 9, 1960 F IG 4 i n v INVENTORS F.J. D F T H El F i G 5 GENT United States Patent Ofifice 3,9623% Patented Nov. 6, 1.962

3,062,302 INDICATOR DEVICE FOR BEARING FAHJURES IN DRHJL BITS Frederick J. Toth, New Orleans, La., and David F. Toomey, Kilgore, Tex., assignors to Shell Oil Company,

New York, N.Y., a corporation of Delaware Filed May 9, 1960, Ser. No. 27,903

6 Claims. (Cl. 17539) This invention relates to drill bits used for drilling wells in earth formations, and pertains more particularly to rock bits that are adapted with a device to transmit a signal to the surface of the earth when the bearings of the bits become heated above a predetermined temperature,

thereby indicating that bearing failure and consequent total bit failure is imminent.

In the drilling of wells into earth formations by the rotary drilling method, particularly in drilling boreholes for the production of oil and gas, the drill bit attached to the lower end of the drill stem is subjected to conditions which cause rapid wear of the cutting elements and the bearings of the rotating cones of the bit. From time to time, at irregular intervals, the teeth or cutting elements on the cones of the bit become dull necessitating pulling the drill stem from the hole, attaching a new hit to the bottom of the drill stem, and then inserting and running the drill stem and bit into the well again. At other times drill bits fail due to failure of the bit bearings with one or more cutters thereon being lost in the hole. In such cases the bit has to be replaced and the pieces of the bit lost in the hole are usually removed by a time-consuming fishing operation, with magnetic or other types of fishing tools, prior to continuing drilling operations.

A driller in charge of well drilling operations attempts to obtain a well-balanced condition between tooth Wear and bearing wear of a roller type bit. Ideally, the degree of tooth wear should equal the degree of bearing wear so that the life of both would terminate about the same time. The driller attempts to achieve equal wear on the teeth and the bearings through proper manipulation of weight on the bit and the speed at which it is rotated. A measure of a drillers skill is his ability to apply and control these drilling variables in a manner so that the teeth become dull at the time bearing life has reached its limit.

It is necessary to anticipate the proper moment to pull or change a bit in order to obtain optimum economic footage, that is, to drill that number of feet of borehole for a given bit which will realize the lowest cost per foot of borehole drilled. Unfortunately, the driller must rely to a large extent upon his knowledge of drilling conditions in order to know when to pull a bit. At present, there is no direct method of determining the condition of a bit in the hole. As a result, many rock bits which are only partially dull are pulled simply because the driller knows that it is better to pull a bit out of the hole early than to take a chance on damaging the bit excessively. Occasionally, even the best drillers guess wrong and, as a result of excessive bearing wear, cones as well as bearings are lost in the hole.

In rock bits, i.e., those having rotatable cutter cones, all bearings and bearing races in the bit are case-hardened through a carburizing process. Case-hardening forms a thin shell of wear-resistant metal on the surface of the bearings and races. Bearing life is determined by the resistance to wear of this case. When the protective case is once worn through to expose the relatively soft underlying metal, the failure or destruction of the remaining case, an action known as spalling, progresses at a rapid rate. Following this, complete failure of a bit generally occurs within a short time. At one stage of bit failure a cone may become locked which causes it to skid on the bottom of a borehole as the bit is rotated. This condition may be indicated at the surface of the earth by a decrease in the penetration rate of the bit. Quite often, however, any decrease in penetration of this type is slight, or a driller may mistakenly interpret it as a change in formation hardness or drillability. This generally results in more or less disintegration of the bit with the accompanying loss initially of the bearings, and ultimately the cone.

It is therefore an object of the present invention to provide a drill bit which, when its bearings have become heated above a predetermined temperature, will cause a change in the fluid pressure in the mud stream pumped through a drill string attached to the bit so as to give a signal to a drilling crew indicating that the drill bit should be removed as failure of the bearings is imminent due to overheating.

Another object of the present invention is to provide an improved drill bit having rotatable cutter cones which is adapted to automatically generate a signal at the bottom of the well and transmit it to the surface to indicate that the temperature of the bearings has passed beyond a predetermined value.

These and other objects of the present invention will be understood from the following description taken with regard to the drawing, wherein:

FIGURE 1 is a graph showing a hypothetical bearing wear and bearing temperature curves plotted against bit rotating time;

FIGURES 2, 3 and 4 are diagrammatic views taken in vertical cross-section through one wall and one cutter cone of a rock bit; and,

FIGURE 5 is a digrammatic view taken in vertical cross-section through one-half of a diamond bit.

One indication of excessive bearing wear in a rock drill bit is a rise in bearing temperature which rises rapidly toward the end of the bit life in some manner such as is shown in FIGURE 1 of the drawing. The operating temperature of the hearings in a bit throughout the major portion of the life of the bit and prior to spalling may be shown as remaining relatively constant, as shown in portion A of the bearing temperature curve, if it is assumed that the drilling variables such as bit rotation speed, weight on bit, hardness and temperature of the formation, temperature and circulation rate of the drilling fluid, etc., remain constant. However, as the hearings or bearing races become worn and spalling occurs, a temperature rise as shown by portion B of the curve, can be expected due to the heat generated by the friction between the irregular bearing and race surfaces. At this stage, the temperature rise should progress at a more or less rapid rate to some temperature shown as C on the curve due to the rapid breakdown of the case hardening, with total bearing failure occuring at some temperature D on the curve.

Referring to FIGURE 2 of the drawing, a rock bit is shown as comprising a bit body it having a threaded portion 11 at the upper end thereof for connection to the lower end of a drill string. A chamber 12 is provided in the upper end of the bit body, the chamber 12 being adapted to receive therein a drilling fluid, commonly known as mud, which is passed downwardly through one or more nozzles 13 at the bottom of the chamber.

integrally formed on the bit body 10 are one or more cone-carrying spindles 14 which are preferably inwardly directed, as illustrated, but may be outwardly directed, as in the case of certain types of reaming bits. Rotatably mounted on the spindle 14 is a rock-cutting cone to having a plurality of teeth or other cutting, grinding, or crushing elements formed on or fixedly attached to the outer face thereof. Suitable bearing means are provided between the rotating cone 16 and its spindle 14. These bearings may be of any suitable type, as for example a set of roller bearings 17 which move in a bearing race 18 in the spindle 14, and roller bearings 19 which move in a raceway 20.

The present invention is directed to a drill bit provided with a suitable temperature-responsive valve adapted to either open or close a fluid port in the body of the bit so as to cause a sudden decrease or increase in the pressure of the drilling mud within the internal chamber 12 of the bit and within the drill stem (not shown) connected to the top of the bit and extending up to the surface of the earth, so that a signal representing any change of pressure in the fluid column is able to be recognized by the driller in charge of well drilling operations. If desired, this increase or decrease in pressure of the mud system may be employed to sound an alarm or trigger a warning light in any manner well known to the art.

One form of a temperature-responsive valve for use in rock drill bits is shown in FIGURE 2 and comprises a ball plug 23 of a diameter slightly larger than the nozzle 13 so that one of the nozzles 13 in the drill bit is closed when the ball plug 23 has been forced into the interior cavity 12 of the bit 10. Various arrangements may be employed for forcing the ball plug 23 into the chamber 12 so that it closes one of the nozzles 13. In FIGURE 2, the bit body 10 is shown as being provided with an internally-threaded horizontally-directed recess 24 into which a cartridge 25 may be inserted and fixedly positioned therein as by screw threads 26, as illustrated. The ball plug 23 fits tightly within the open end of the cartridge 25 in front of a temperature-responsive explosive charge 27. The ball plug 23 which is pressed into the open end of the cartridge 25 acts as a seal for the powder charge 27, or another type of a seal, such for example as a plastic film, may be employed between the explosives 27 and the ball 23 to protect the explosive against moisture. If desired, a certain amount of primer may be positioned in a tube 28 extending from the cartridge 25. The outwardly extending end of the tube 28 is secured by any suitable type of connector 29 to a temperature-sensing and heat-transmitting triggering mechanism which may take the form of a conductor tube 30 which is preferably a metal tube having a high coefficient of conductance, such as silver. It is essential that the lower end of the temperature-sensing and heat-transmitting conductor tube 34 extend down into the bit spindle 14 in the vicinity of the bearings 17 and 19.

In operation of the present invention in accordance with the embodiment described with regard to FIGURE 2, as the bearings 17 and 19 become overheated due to spalling action the heat is transmitted through the spindle 14 to the metal conductor tubing 39 which conducts heat to the explosive charge 27 contained in the cartridge 25. When the transmitted heat explodes the explosive charge 27, the ball plug 23 is forced into the fluid course 21 and seats itself on the shoulder 31 at the entrance of the fluid discharge nozzle 13 where fluid pressure holds the ball plug in place. Upon closing one of the nozzles 13, a sudden build-up of pressure fluid within the chamber 12 of the bit 10 in the drill string thereabove is created which is easily recognizable at the surface by any suitable pressure indicating means, such as a gauge, or by a light or horn alarm system. Since apparatus for indicating, recording and transmitting pressure changes are well known to the art, as well as alarm systems which are energized or triggered by a change in pressure, such systems will not be further described here as they do not constitute a novel part of the present invention.

Various other types of valve-actuating apparatus may be employed. For example, as shown in FIGURE 3, a compression spring 35 is employed to eject the ball plug 23 out of the cartridge 25. The spring 35 is held in compression by means of a plate 36 which is anchored by means of a fusible plug 37 to the back of the cartridge 25 and in contact with the heat transmitting conductor tube 30. The operation of the apparatus shown in FIGURE 3 is much similar to that described with regard to the apparatus of FIGURE 2. However, in the apparatus of FIGURE 3, instead of employing a powder charge which is designed to burn at a predetermined temperature, as shown in FIGURE 2, the fusible plug 37 of FIGURE 3 is designed to melt at the same temperature to release the compression spring 35 and allow it to propel the ball valve 23 into the water course 21 to close a nozzle 13. The fusible plug 37 is preferably selected to melt at some temperature C, as shown in FIGURE 1.

In the apparatus as shown in FIGURES 2 and 3, the discharge of the ball plug 23 so as to block one of the nozzles 13 results in an instantaneous measurable pressure increase in the circulating mud system. However, it is to be recognized that a sudden decrease in the pressure of the circulating mud system could also be utilized as a warning signal to indicate that the bearings of the drill bit at the bottom of the hole were at a dangerous temperature. Thus, in FIGURE 4 the cartridge 25 positioned in the recess 24 is provided with readily disintegratable closures 40 and 41 at opposite ends which may be readily destroyed by ignition of the explosive charge 27 while at the same time being sufliciently rigid enough to withstand normal pump pressures of the circulating mud system through the bit. In the arrangement shown in FIGURE 4, when the bearings 17 and 19 and the spindle 14 have become heated to a dangerous temperature, heat will be transmitted up the conductor tube 30 to ignite the explosive charge 27 and destroy both ends 40 and 41 of the cartridge 25. Thus, the recess 24 will be completely open to the flow of fluid, allowing fluid in the hollow interior 12 of the bit 10 to be discharged horizontally through the recess 24. This will cause a sudden decrease in the pressure of the circulating mud system which will be easily recognizable or measurable at the surface.

Another arrangement of a drill bit provided with a temperature indicating means is illustrated in FIGURE 5 wherein a diamond bit is shown. Diamonds are held on the outer surface of a diamond drill bit by a matrix and costly diamond losses generally result from the overheating and subsequent melting of the matrix. It is therefore a further object of the present invention to provide a suitable temperature-indicating means for a diamond drill bit to give an indication when the temperature of the matrix of the bit has reached a dangerous level.

As shown in FIGURE 5, a bit body 45 has a plurality of diamonds 46 mounted on the outer surface thereof by means of a matrix. A conductor tube is arranged to extend down through the body 45 of the bit to a point near the lower face of the bit in order to obtain a measure of the temperature of the bit near the bottom face which is rotating against the bottom of a well borehole. The top of the conductor tube 47 is in contact with a primer 48 positioned within the explosive charge 49 of the cartridge 50. The cartridge 50 is positioned in a horizontal recess 51 in the body of the bit and contains a ball plug 52 adapted to be discharged into the chamber 53 within the bit so that it drops down and closes the nozzle 54 through which circulating drilling fluid is discharged through the bottom of the bit. Closing of the nozzle causes an instantaneous build-up of pressure within the valve and the drill string extending thereabove, which pressure increase is readily identifiable at the surface.

Although the present invention has been described with regard to using a single conductor tube 30 of FIGURE 2 extending into a single spindle 14, it is recognized that if desired a similar conductor tube may extend into each of the spindles of the drill bit with all of the conductors tubes being preferably connected to a single cartridge rather than to individual cartridges. Likewise, while the present invention has been described with regard to FIG- URE 2 as having a conductor tube 30 of silver for transmitting heat to the explosive charge 27 of the cartridge 25, it is to be appreciated that the conductor tube 30 itself may be filled with a powder charge, or preferably a primer charge, which would be fired when the temperature of the spindle 14 reached a predetermined temperature, preferably at temperature C on FIGURE 1. The use of a primer charge in the conductor tube 30 would then eliminate any delay in the transmission of heat to the explosive charge.

With regard to FIGURE 3, instead of element 37 being a fusible plug which anchors the plate 36 to the back of the cartridge, this element 37 may be a brittle member or one that is easily broken upon extension. Thus, if element 37 was in communication with the conductor tube 30 which was in turn filled with an expansible liquid or solid material which could expand at a predetermined temperature causing the hollow element 37 to be ruptured so as to release the compression spring which would force the ball 23 out of the recess 24. Compounds are commercially available which could be used to fill the conductor tube 30 of FIGURE 3, these compounds having a property of melting abruptly at a predetermined temperature and undergoing an increase in volume.

We claim as our invention:

1. A drill bit comprising a hollow body releasably connectable to a drill stem adapted to be in communication with a source of drilling fluid under pressure, the bit body being provided with port means therethrough for discharging fluid therefrom, rock-cutting means carried on the bottom of said bit body, valve means carried within said body for altering the flow of fluid from the port means thereof, and temperature responsive valve-actuating means positioned adjacent said valve means and having a temperature-sensing and heat transmitting portion thereof extending into the lower portion of said bit to a point adjacent the rock-cutting means.

2. A rock drill bit comprising a hollow body releasably connectable to a drill stem adapted to be in communication with a source of drilling fluid under pressure, the bit body being provided with port means therethrough for discharging fluid therefrom, said body having a plurality of cone-carrying spindles formed on the outside of said body, a cutter cone rotatably mounted on each of said spindles, rock-cutting means formed on the outer face of said cutter cones, bearing means carried by said bit between each of said cones and the spindle on which it is mounted, valve means carried within said body for altering the flow of fluid from the port means thereof, and temperature-responsive valve-actuating means positioned adjacent said valve means and having a temperaturesensing and heat transmitting portion thereof extending into at least one of said spindles to a point adjacent the bearing means.

3. A rock drill bit comprising a hollow body releasably connectable to a drill stem adapted to be in communication with a source of drilling fluid under pressure, the bit body being provided with port means therethrough for discharging fluid therefrom, said body having a plurality of rock-cutting diamonds set on the outer face of said bit, valve means carried within said body for altering the flow of fluid from the port means thereof, and temperature-responsive valve actuating means positioned adjacent said valve means and having a temperature-sensing and heat transmitting portion thereof extending into said bit body to a point adjacent the diamonds. I

4. A rock drill bit comprising a hollow body releasably connectable to a drill stem adapted to be in communication with a source of drilling fluid under pressure, the bit body being provided with port means therethrough for discharging fluid therefrom, said body having a plurality of cone-carrying spindles formed on the outside of said body, a cutter cone rotatably mounted on each of said spindles, rock-cutting means formed on the outer face of said cutter cones, bearing means carried by said bit between each of said cones and the spindle on which it is mounted, valve means carried within said body for altering the flow of fluid from the port means thereof, valve means carried within said body for at least partially closing said normally-open port means, a temperature-responsive explosive charge positioned adjacent said valve means for actuating said valve means, and temperature-sensing and heat transmitting means in firing contact with said explosive charge and extending into at least one of said spindles to a point adjacent the bearing means.

5. A rock drill bit comprising a hollow body releasably connectable to a drill stem adapted to hem communication with a source of drilling fluid under pressure, the bit body being provided with normally-open port means and normally-closed port means therethrough for discharging fluid therefrom, said body having a plurality of conecarrying spindles formed on the outside of said body, a cutter cone rotatably mounted on each of said spindles, rock-cutting means formed on the outer face of said cutter cones, bearing means carried by said bit between each of said cones and the spindle on which it is mounted, valve means carried within said body for altering the flow of fluid from the port means thereof, said valve means carried within said body for opening said normally-closed port means, a temperature-responsive explosive charge positioned adjacent said valve means for actuating said valve means, and temperature-sensing and heat transmitting means in firing contact with said explosive charge and extending into at least one of said spindles to a point adjacent the bearing means.

6. A rock drill bit comprising a hollow body releasably connectable to a drill stem adapted to be in communication with a source of drilling fluid under pressure, the bit body being provided with port means therethrough for discharging fluid therefrom, said body having a plurality of cone-carrying spindles formed on the outside of said body, a cutter cone rotatably mounted on each of said spindles, rock-cutting means formed on the outer face of said cutter cones, bearing means carried by said bit between each of said cones and the spindle on which it is mounted, valve means carried within said body for altering the flow of fluid from the port means thereof, said valve means being spring loaded and carried within said body for at least partially closing said normally-open port means, temperature destructible means normally retaining said valve means in an inoperative position, and temperature-sensing and heat transmitting means in thermal contact with said temperature destructible means and extending into at least one of said spindles to a point adjacent the bearing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,246,536 Reinthaler June 24, 1941 2,457,960 Walker Jan. 4, 1949 2,560,328 Bielstein July 10, 1951 2,633,025 Boice et a1. Mar. 31, 1953 2,798,764 Ray July 9, 1957 

